A precise correcting method for the study of the superhard material using nanoindentation tests

The accurate description of the indentation load-displacement relationship of an elastic sharp indenter indenting into an elastic half-space is critical for analyzing the nanoindentation data of superhard materials using the procedure proposed by Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)]. A further discussion on this issue is made in the present work to reconcile the apparent inconsistencies that have appeared between the experimental results reported by Lim and Chaudhri [Philos. Mag. 83, 3427 (2003)] and the analysis performed by Fischer-Cripps [J. Mater. Res. 18, 1043 (2003)]. It is found that the indenter size effect is responsible for this large discrepancy. Moreover, according to our analysis, we found that when the deformation of the indenter is significant, besides the errors caused by the Sneddon's boundary condition as addressed by Hay et al. [J. Mater. Res. 14, 2296 (1999)], the errors induced by the application of reduced modulus should be considered at the same time in correcting the modified Sneddon's solution. In the present work, for the diamond indenter of 70.3° indenting into an elastic half-space with its Poisson's ratio varying from 0.0 to 0.5 and the ratio of the Young's modulus of the indented material to that of the diamond indenter, E_material/ E_indent_er varying from 0 to 1, a set of new correction factors are proposed based on finite element analysis. The results reported here should provide insights into the analysis of the nanoindentation load-displacement data when using a diamond indenter to determine the hardness and Young's modulus of superhard materials. © 2007 Materials Research Society.